Osmosis detection will be the basic principle of the spring of dip coating (penetrant) some penetration ability of the solution, the infiltration of surface defects, and then to remove excess penetrant, appeared in the surface layer of the tu yi agent again, at this point defects remaining in the penetrant sucked out, under the purple pay-off (fluorescence) observation or direct observation, can be found that the existence of defects.Osmotic detection can be used for the detection of ferromagnetic springs as well as non-ferromagnetic materials such as copper alloy and austenitic stainless steel springs.
(1) oil immersion test can be used for spring whose diameter of wire is greater than 8mm.The spring that has been cleaned on the surface is immersed in kerosene, or the mixture of 50% (mass fraction) kerosene and 50% (mass fraction) l-an32, and soaked for about 20min (appropriately increasing the oil temperature can shorten the soaking time, but the oil temperature is limited to 80~C).When soaking, the oil will infiltrate into the cracks and other defects, after the oil soaked spring sandblasting to remove all the oil, check the spring surface, can identify the cracked spring.
(2) fluorescence detection is suitable for large springs and smaller springs. The method is similar to that of oil immersion detection, except that oil is changed to permeate agent containing phosphor powder.Fluorescent materials show bright color traces under near ultraviolet light, so it is easy to find cracks or other open defects.As the osmotic agent benzene is poisonous, it should be protected.
(3) the staining method is composed of three solutions: cleaning solution, osmotic solution and display solution.When using surface to be tested first washed with cleaning fluid, then penetrating fluid jet to test parts of the spring, wait a moment, for penetrating fluid infiltration defects, then use clean surface cleaning fluid, finally to show agent injection to the surface of the spring, defects can be displayed, in order to make the defect marked, according to general penetrants in red.
The permeation test shows a width of 0.The defect of 01mm is easy to operate and easy to use.But the disadvantages are low efficiency, the solution can not be recycled, high cost, and only surface opening defects can be found.
